A storage area network (SAN) is a network designed to attach computer storage devices such as disk array controllers and tape libraries to servers. One common SAN design utilizes a plurality of fibre channel (FC) switches which are operatively coupled using inter-switch links (ISL) to form a fabric, such as in an FC-SW topology. The fabric elements (e.g., the fibre channel switches) provide connections between nodes. The nodes are the end devices (e.g., servers or data storage devices) connected to the fabric.
In order to manage the operation of a SAN, it is important that the network administrator be able to monitor data traffic through the fabric. For example, an error in the fabric may cause a loss of communication between two nodes. The network administrator must then identify the source of the problem in order to correct this problem. Various tools have been developed to assist the network administrator in doing so.
For example, a Switched Port Analyzer (SPAN) function has been developed which enables non-disruptive monitoring of network traffic through one or more ports of an FC network device. The SPAN function enables traffic through any FC interface of the FC network device to be replicated and delivered to a port on that FC device. A similar feature, Remote Switched Port Analyzer (RSPAN), enables the replicated traffic to be delivered to a port on a remote network device. Both the SPAN and RSPAN functions are useful for network administration, intrusion detection, and network analysis. However, the configuration of the SPAN and RSPAN functions must be performed on each individual switch. Thus, if the location of an error within a fabric is unknown, it can be time-consuming to monitor each individual switch in order to discover the source of the error. In addition, the path followed by a frame transmitted between two nodes may change dynamically due to changes in the Fabric Shortest Path First (FSPF) configuration.
Another function used for troubleshooting FC fabrics is the FCTrace function. FCTrace is used to determine characteristics associated with routes in a fibre channel network by sending special frames between a source and a destination. Timestamp information is inserted into these special frames at each FC switch through which the frames travel. Once the frames reach the edge of the fabric (the F port or FL port coupled to the destination end node), the frames are routed back to the source node. The timestamp information can enable an administrator to determine characteristics, such as round trip times, inter-switch latency, and connectivity to a destination node for specific routes. Unfortunately, in many cases, the connectivity between two nodes may be broken, but the FCTrace results indicate that the fabric connectivity is operating correctly. This situation may result because FCTrace uses special frames which may undergo different forwarding, network address translation (NAT), and access control decisions compared to actual data frames.
Accordingly, it would be desirable to provide network administrators the ability to easily and accurately monitor network traffic.